Without a full memory barrier between the store to the flags and the
load of the SQ tail the two operations can be reordered and this can
lead to a situation where the SQPOLL thread goes to sleep while the
application writes to the SQ tail and doesn't see the wakeup flag.
This memory barrier pairs with a full memory barrier in the application
between its store to the SQ tail and its load of the flags.
Signed-off-by: NAlmog Khaikin <almogkh@gmail.com>
Link: https://lore.kernel.org/r/20220321090059.46313-1-almogkh@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>